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Lipids

Lipids

Author: Sophia Tutorial
Description:

Understand the elements and behavior of lipids.

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Tutorial
what's covered
In this lesson, you're going to learn about the different types of lipids and their structure and function in your body. Specifically, you will look at the following:
  1. Lipid Characteristics Overview
  2. Fats
    1. Saturated Fats
    2. Unsaturated Fats
  3. Triglycerides
  4. Phospholipids
  5. Sterols

1. Lipid Characteristics Overview

Lipids are molecules that are nonpolar. They contain hydrogen, carbon, and oxygen. They are an organic molecule. They also don't dissolve in water, which goes along with them being nonpolar.

terms to know
Lipid
An organic molecule made up of fatty acids, which is nonpolar, and does not dissolve easily in water.

Nonpolar
Does not dissolve easily in water.

2. Fats

Fats are a type of lipid that have at least one fatty acid tail attached to a glycerol molecule.

A glycerol molecule can have up to three side chains. If it has at least one fatty acid for a side chain, the molecule is a fat.

There are two main categories of fats: Saturated fats and unsaturated fats.

term to know

Fat
A lipid made of a glycerol molecule and at least one fatty acid side chain.

2a. Saturated fats

Saturated fats are a type of fat that only contain single covalent bonds in the fatty acid tail.

Often saturated fats are animal fats. Because there are no double bonds, the fatty acid side chains are fairly straight and therefore can pack together neatly. This dense packing is the reason when saturated fats tend to be solid at room temperature. An example of a saturated fat would be lard.

File:7240-Saturated_Fats.png

term to know

Saturated Fat
A type of fat which does not have double bonds in its side chain.

2b. Unsaturated fats

Unsaturated fats are a type of fat that has one or more double covalent bonds between carbons, which are the backbone of the fatty acid.

Unsaturated fats are generally more plant-based, whereas saturated fats are more animal-based. The double bond puts a kink in the fatty acid chain, so saturated fats can't pack together very tightly. Because of this less dense packing, unsaturated fats tend to be liquid at room temperature. An example of an unsaturated fat might be vegetable oil or olive oil.

File:7241-Unsaturated_Fats.png

Each "C" in the pictures is a carbon, each "H" is a hydrogen, and each "O" is an oxygen.

Unsaturated fats are also generally a little bit healthier than saturated fats. However, there are some unsaturated fats, such as trans fats, that are unhealthy.

Like other unsaturated fats, trans fats have a double bond between at least two of the carbons ("C" in the pictures). Unlike other unsaturated fats, this double bond doesn't put a kink in the chain. The fatty acid chains remain fairly straight and pack densely like saturated fats.

Another type of unsaturated fat is something called polyunsaturated fat. The prefix "poly" means many; this type of unsaturated fat could have multiple double bonds.

term to know
Unsaturated Fat
A type of fat which has double bonds in its side chain.

Trans Fat
A type of unsaturated fat which may lead to health problems.

3. Triglycerides

Triglycerides look similar in structure to fats, but the prefix "tri" means three, so rather than just having one fatty acid tail, they have three. Triglycerides are the most common lipid in your body and contain lots of energy. An example of a triglyceride might be butter, lard or oils.

File:7242-Screen_Shot_2018-12-29_at_10.19.15_PM.png

term to know

Triglyceride
A type of lipid which is made up of a glycerol molecule and three fatty acid side chains.

4. Phospholipids

Phospholipids are a type of lipid found in the cell membrane of your body's cells. Phospholipids are made up of a hydrophilic (polar, water-attracting) head and two hydrophobic (non-polar, water-repelling) tails.

Something that is hydrophilic is attracted to water, whereas something that is hydrophobic is repelled by water. So in the structure of your cell membranes, the phospholipids are arranged in a bilayer.

See the image of a phospholipid below.

File:7239-Phospholid_tail_head.png

The head faces out and all of the tails face in. The heads are hydrophilic, meaning they're attracted to water. So those heads are pointed to the outside, or to the inside of the cell, where there's water. The hydrophobic tails are pointed inward, away from water.

term to know

Phospholipid
A type of lipid made up of a hydrophilic head and hydrophobic tail and is found in cell membranes.

5. Sterols

Sterols are lipids that don't have glycerol so their structure is a little bit different. The fatty acids, instead of being side chains, often form into multiple rings. Instead of 1 to 3 "chain ropes," the fatty acids look more like "chain mail."

File:7243-Sterol.svg

EXAMPLE

One common example of sterols would be cholesterol in your body. Steroid hormones, like estrogen and testosterone, are also examples of sterols.

term to know

Sterol
A type of lipid containing only fatty acids.

summary
This lesson has been an overview of the different types of lipids, and the structure and function of them in your body. In this lesson, you learned that lipids are nonpolar, and don't dissolve in water. They are organic molecules containing hydrogen, carbon, and oxygen. You also went more in-depth about fats, triglycerides, phospholipids, and sterols. Keep up the learning and have a great day!

Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

Attributions
  • Phospholipid | Author: Wikipeda | License: Creative Commons
  • Sterols | Author: Wikipeda | License: Public Domain
Terms to Know
Fat

A lipid made of a glycerol molecule and at least one fatty acid side chain.

Lipid

An organic molecule made up of fatty acids, which is nonpolar, and does not dissolve easily in water.

Nonpolar

Does not dissolve easily in water.

Organic Compounds

Compounds that contain the element carbon.

Phospholipid

A type of lipid made up of a hydrophilic head and two fatty acids (hydrophobic tail) and is found in cell membranes.

Saturated Fat

A type of fat which does not have double bonds in its side chain.

Sterol

A type of lipid containing only fatty acids.

Trans Fat

A type of unsaturated fat which may lead to health problems.

Triglyceride

​A type of lipid which is made up of a glycerol molecule and three fatty acid side chains.

Unsaturated Fat

​A type of fat which has double bonds in its side chain.